TH-K2AT/K2E/K2ET

CIRCUIT DESCRIPTION

■CTCSS/DCS

The encode signal is generated by the MPU (IC8) and output from the TONE terminal (pin 41) of the MPU.

The unwanted high-frequency components of the encode signal output from the MPU are removed with a low-pass filter, and applied to VCO modulation input (MOD) and TCXO VC terminal for modulation.

The VCO and TCXO modulation levels are adjusted by VR6 to produce flat modulation characteristics in low and high ranges.

The decode signal is input to the SIGIN pin (pin 47) of the MPU after the waveform of the audio signal from the FM IC is rectified with a CTCSS/DCS filter (IC17). Then the set CTCSS tone frequency and DCS code are detected by digital signal processing in the MPU to control muting.

■DTMF

The DTMF signal is generated by the MPU (IC8) and is output from the DTMF/BEEP terminal (pin 40) of the MPU.

The DTMF signal is mixed with an audio signal at the input side of the AF amplifier (IC6), and is output as a monitor tone.

The DTMF signal is mixed with a modulation signal at the input side of pre-emphasis in the microphone amplifier (IC16) and used as a transmit signal.

■VOX

The IC5 and Q30 amplify the audio signal captured in the microphone, and then the signal is converted into the DC Voltage D24 rectifies.

The DC voltage activates the MPU (IC8), and the VOX starts.

VCO

MOD

X1

 

 

■ Weather Alert (K and K2 types only)

TCXO

 

 

 

The IC17 apmlifies the detected signal from the FM IC (IC3),

VC

 

 

and the MPU (IC8) processes the signal. This signal processing

VR6

 

LPF

activates Weather Alert function.

 

 

 

 

 

 

 

 

 

41

 

 

 

 

 

Q30 D24

TONE

IC17

IC3

 

 

50

VOX IN

47

CTCSS/DCS

9 FM

 

 

AMP

SIG IN

FILTER

IC

 

 

 

 

 

VR5

1

 

IC8

111

 

 

 

MPU

 

 

MIC

 

NOAA

K, K2 types only

 

 

 

IC16

DTMF/BEEP

 

 

 

AMP

 

 

 

 

6

 

40

 

 

 

VOL OUT

IC5 MIC

 

 

 

 

 

 

 

 

 

IC6

 

HPF

 

 

 

 

AF AMP

 

 

 

 

 

 

Vin

 

 

 

 

 

 

Fig. 15 CTCSS/DCS, DTMF, VOX, Weather alert

■Serial Control

Serial control must be enabled from a transceiver menu so that the REM/TXD pin of the speaker jack (J4) and the PTT (RXD) pin of the microphone jack (J3) function as TXD and RXD, respectively, when communicating with a personal computer.

J3

MIC JACK

J4

SP JACK

 

5MC

 

 

IC5

 

 

 

HPF

 

 

 

PTT

 

 

 

MIC

 

 

 

IM

+

MIC

 

 

–

 

5MS

 

 

 

 

 

SPG

 

13

 

 

PTTE

 

REM/TXD

 

 

 

46

 

SPK

 

REM

TXD 12

10 POUT

 

AFO

IC8

11

 

 

MPU

RXD

 

 

 

IC6

AF AMP

SP

Fig. 16 Serial control

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